1. Field of the Invention
Methods and apparatus consistent with the present invention relate to image encoding and decoding, and more particularly, to image encoding and decoding capable of improving image compression efficiency by using human psycho-visual characteristics.
2. Description of the Related Art
FIG. 1 illustrates an example of a related art prediction-based image encoding method.
Referring to FIG. 1, in video compression standards such as MPEG-1, MPEG-2, MPEG-4 Visual, H.261, H.263, and H.264, one frame is divided into a plurality of macro blocks, a prediction process is performed on a macro block basis to obtain a predicted block P corresponding to a current block O, a residual block, which is a difference between the current block O and the predicted block P, is transformed and quantized to reduce the range of a transform coefficient, and entropy coding is then performed.
In a conventional prediction-based image encoding method, a predicted block, i.e., the most similar block to a current block, is obtained by using spatio-temporal correlation of an image in an optimum manner. In the related art prediction-based image encoding method, compression efficiency is enhanced by coding a residual signal that is a difference between the current block and the predicted block. Eventually, in the related art image encoding method, the compression efficiency is determined based on the degree of similarity between the current block and the predicted block.
However, the related art method does not properly use the characteristics of the human visual system when an image is encoded. According to the related art method, a residual block or an entire transformed block is encoded as it is including a portion which cannot be easily visually noticed by a user. In order to overcome a limit in a transfer bandwidth and to provide a high definition image to the user, there is a need for an image encoding method having further improved compression efficiency.